Refrigerating compressor



United States Patent 3,201,67 6 REFRIGERATING COMPRESSGR Richard E. Fuhrman, York, Per, assi ns: to iiorgWarner This invention relates to hermetic refrigerating compressors. The invention more particularly relates to a means and method for providing a'source of heat Within the compressor to insure the vaporization of any liquid refrigerant therein.

7 In a typical refrigerating system when the system is shut down, refrigerant within the system tends to flow to the coldest part of the system where it remains in a liquid state. In those systems wherein the compressor, for example, may be at an ambient which is colder than the primary part of the system, then, as pointed out above, the refrigerant tends to flow to the compressor and collect therein. Such a situation could arise, for example, wherein an occupied space has a high internal heat load even in the wintertime and requires air conditioning during the day. If the compressor is located outdoors, it would be apparent that at night, when the system is shut down, the compressor becomes the coldest part of the system.

The liquid refrigerant in the compressor has several undesirable effects: one, when the compressor is started up, since it is adapted to handle gas and not liquid, valve breakage is very apt to occur; two, the liquid refrigerant would have a tendency to dissolve the lubricating oil with a consequent .loss of lubricating properties to the further detriment of the machine; and three, the liquid refrigerant apparently undesirably reduces the resistance of certain types of electrical insulation such as Fermi/211" or cellulose used on the motor windings.

It is an object of the invention, therefore, to provide, in'a hermetic refrigerating compressor, a source of heat to insure that any liquid refrigerant that may be found therein becomes vaporized.

It is a further object of the invention to provide, in a hermetic refrigerating compressor, means for energizing the running windings of the compressor motor from a low voltage source, when the motor is at rest, to heat the windings, thereby vaporizing any refrigerant Within the compressor.

It is a further object to provide a hermetic refrigerating compressor, as set out above, wherein the running windings of the compressor motor are automatically energized from the low voltage source whenever the compressor motor is inoperative.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above-stated objects and such other objects as will appear from the following description of preferred embodiments of the invention described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a typical refrigerating system including a hermetic compressor embodying the invention; and

FIG. 2 is a wiring diagram showing how the invention is to be applied to a typical hermetic compressor motor.

Turning now to FIG. 1, the refrigerating system comprises a hermetic compressor assembly indicated generally at 10 and including a motor section 11 and a primary compressor section 12. A condenser indicated generally at 13 and including a coil section 14, and an evaporator indicated generally at 15 and inciuding a coil section 16 complete the main components of the system. A fan 17 driven by a motor 18 is provided for circulating ambient air over condenser coil lid. A fan l9 driven by a motor 20 is provided for circulating the air to be conditioned over the evaporator coil 16. Coil 14 is connected to the hermetic compressor 10 by way of a hot gas line 21. Evaporator coil 16 is connected to the hermetic compressor 10 by way of a cold gas line A liquid line 23, including a capillary 24, connects the two coils 14 and 16. A thermostat 25 serves to open and close a switch 25a to control the operation of the refrigerating system. Thermostat 25 is mounted on a wall 26 of the space to be conditioned.

It will be appreciated that coil 14 may be cooled by a liquid such as water and that coil 16 may be utilized for conditioning a heat-exchange fluid rather than air, and both would be within the ambit of the herein-described invention. Also, as shown in FIG. 1, the evapora tor is located within the space to .be conditioned defined by the wall 26. It will be appreciated, of course, that evaporator 15 could be located outside of the conditioned space with the conditioned fluid being delivered thereto.

Turning now to FIG. 2, the electrical system will be set out. Lines L-ll, L-2 and L-3, controlled by a master switch 2'7, serve to conduct electrical power, from whatever source deiived, to motor 11. The operation of motor ii is controlled by a switch indicated generally at 28 having switch arms 29, 3i 3% and 31. A solenoid 32, including solenoid windings 33, operates switch 28. Overload contacts 34 and 35 and a high pressure cutout switch 36 provide the necessary safety features. Solenoid winding 33, overload contacts 34 and 35, high pressure cutout switch 36 and thermostatically controlled switch 25a are connected in series across lines L-1 and L2 through a switch 37 as follows: a lead 38 connects line L-i. with one side of switch 37. The other side of switch 37 is connected by lead 39 to one side of thermostatically controlled swtich 25a. The other side of switch 25a is connected by way of a lead 40 to one side of high pressure cutout switch 36. The other side of switch 36 is connected by a lead 41 to overload contact 34. Lead 42 connects overload contact 34 to overload contact 35. A lead 43 connects overload contact 35 to solenoid winding 33. Lead 44 runs from solenoid winding 33 to line L-Z to complete the circuit. Heaters 45 and 46 are provided respectively in lines L3 and L1 in close proximity to overload contacts 34 and 3d. When too much current flows, heaters 45 and 46 reach a temperature sufficiently high to open switches 34 and 35 breaking the circuit. Since this represents standard motor practice, the above description is believed adequate.

Fan motor 18 is controlled by a switch 47. Motor 18 and switch 27 are connected by a lead 48. The other side of switch 4.7 is connected to line L-f by the lead 38. Fan 1.; is connected into the lead 44, which connects to line L2, by a lead 49. Fan motor 2% is controlled by a switch 559 connected thereto by a lead 51. Switch 50 is connected to line L-1 by way of the aforementioned lead 33 and fan 2%) is connected to the lead 49 by way of a lead 52.

A transformer 53 of any suitable type is utilized for providing low voltage current to the windings of motor '11 when the compressor is shut down. Transformer 53 includes the customary primary windings 54 and secondary windings 55. Primary windings 54 are connected to line L-l by way of a lead 56, the switch arm 31 and a lead 57. The other side of primary windings 54 are connected to line L-Z by a lead 58. One side of secondary windings 55 is connected to the motor windings by a lead 59. The other side of secondary windings 55 is connected to the windings of motor 11 by a lead 60, including a potential relay operated switch 61 operated by a solenoid 62. Solenoid 62 is connected across leads 59 and by leads 63 and 64.

Operation The normal operation of the system is as follows: switches 47 and 50 are closed placing fan motors 18 and in operation. Switch 37 is then closed. Assuming that some cooling is called for within the conditioned space, then switch a is closed by thermostat 25 in a conventional manner (not shown) and a circuit is set up between lines L-l and L-2 as follows: current flows from line L1 through lead 38, switch 37, lead .39, now closed switch 2511, high pressure cutout 36, overload contacts 34 and 35, lead 43, solenoid winding 33 and lead 44 to line L-Z. With the flowing of current through solenoid winding 33, solenoid 32 is energized and switch 28 is actuated to the left, as viewed in FIG. 2, closing the circuit through lines L-l, L2 and L-3 to motor 11 and, at the same time, breaking the circuit through switch arm 31 to transformer 53.

With motor 11 in operation, compressor 12 functions to force high pressure gaseous refrigerant through hot gas line 21 and condenser coil 14 where it gives up its heat to the air flowing thereover under the influence of fan 17 and becoming condensed thereby. The now liquid refrigerant flows through liquid line 23 and capillary 24 whereby its pressure and corresponding temperature are influence of thermostate 25 when no further cooling is needed. Under either of these circumstances, the circuit through solenoid winding 33 is broken and solenoid 32 is de-energized actuating switch 28 to the position shown in FIG. 2. The circuit through lines L-ll, L-2 and L4) to compressor motor 11 is broken and, at the same time, the circuit through primary winding 54 of transformer 53 is closed through switch arm 31. The current induced in the secondary windings 55 then flows through the motor windings to provide a source of heat to vaporize any liquid refrigerant accumulating therein.

On actual tests run on a 7 /2 horsepower, 220 volt, 3 phase, 60 cycle motor it was found that a 70 F. rise in temperature above an ambient temperature'of 80 F. could be maintained with volts supplied to the motor windings resulting in a current flow of 10 ampres and a power consumption of 120 watts. With 27 volts applied to the windings, a 35 F. temperature rise above the 80 F. ambient temperature was maintained resulting in a current flow of 7 ampres and a power consumption of 65 watts.

The voltage impressed on the motor windings by the transformer must be sufliciently low for the motor not to turn over, and also sufficiently low so that no more heat will be generated than is needed to vaporize the refrigerant and yet do no damage to the windings.

It will be noted that on the re-energization of solenoid 32 that switch arm 31 first breaks the circuit through transformer 53 before the circuit to motor 11 is made. It will be apparent that the reverse also is ture, that is, on de-energization of solenoid 32 the circuit to the motor 11 is broken prior to the making of the circuit through transformer 53.

The solenoid 62 is of the type that does not become operative to open the switch 61 until some predetermined voltage is applied thereto. In this instance, the solenoid 62 is selected such that it does not become operative to open the switch 61 until a'voltage slightly higher than the transformer secondary voltage is reached. The switch 61, therefore, normally remains closed so long as motor 11 is de-energized and while transformer 53 is energized. When the motor '11 is operating on normal voltage, the solenoid 62 is operative to open switch 61 to break the circuit to the transformer secondary windings. When motor 11 is de-energized and before it comes to a complete standstill, it can act as a generator setting up a back EMF. in transformer 53 to the detriment of the system. So long as this back is greater than the voltage at which the solenoid 62 is designed to operate, however, then the solenoid 62 maintains the switch 61 open allowing no current flow through the transformer secondary windings, acting as a safety feature in this respect. When the speed of the motor has become reduced to such a point that the back produced is below the'voltage at which the solenoid 62 is operative to maintain switch 61 open, then the switch 61 assumes its normally closed position, closing the circuit through the transformer 53.

. It will be apparent that I have provided a method and apparatus capable of performing its intended function efficiently, automatically and at a very low cost.

I wish it to be understood that my invention is not to be limited to the specific constructions and arrangements shown and described, except only insofar as the claims may be so limited, as it will be apparent to those skilled in the art that changes may be made without departing from the principles of the invention.

1 claim:

1. In a refrigerating compressor assembly. of the type wherein the compressor and its associated motor are hermetically sealed within a casing, an electrical system comprising windings for said motor, a source of electrical energy connected with said windings in an electrical circuit, a transformer including primary and secondary windings, means connecting said secondary transformer windings and said motor windings in an electrical circuit, means connecting said primary transformer windings and said source of electrical energy in an electrical circuit, switch means for breaking the circuit between said electrical source and said primary transformer windings while making the circuit between said electrical source and said motor windings or for alternately breaking the circuit between said electrical source and said motor windings while making the circuit between said electrical source and said primary transformer windings,

normally closed switch means in said circuit between said secondary transformer windings and said motor windings, and means operative to open said switch to break said circuit upon a predetermined voltage being applied to said circuit.

2. The electrical system of claim 1 wherein said first mentioned switch means further includes means for breaking the circuit between the electrical source and the primary transformer winding prior to making the circuit between the electrical source and the motor winding, and alternately for breaking the circuit between the electrical source and the motor winding prior to making the circuit between the electrical source and the primary transformer winding.

References Cited by the Examiner UNITED STATES PATENTS 2,107,887 2/38 Davenport 62-193 2,145,354 1/39 Hull 62--193 2,167,018 7/39 Wolfert 62226 2,175,913 10/39 Philipp 62468 2,338,518 1/44 Koch 318558 2,500,298 3/50 Smith 62155 2,512,342 6/50 Tarkin 310.68.3

FOREEGN PATENTS 700,028 12/ 30 France. 527,448 10/40 Great Britain.

OTHER REFERENCES Electrical World, January 1942, Volume 117, pp. 88 and 90.

ROBERT A. OLEARY, Primary Examiner. 

1. IN A REFRIGEATING COMPRESSOR ASSEMBLY OF THE TYPE WHEREIN THE COMPRESSOR AND ITS ASSOCIATED MOTOR ARE HERMETICALLY SEALED WITHIN A CASING, AN ELECTRICAL SYSTEM COMPRISING WINDINGS FOR SAID MOTOR, A SOURCE OF ELECTRICAL ENERGY CONNECTED WITH SAID WINDINGS IN AN ELECTRICAL CIRCUIT, A TRANSFORMER INCLUDING PRIMARY AND SECONDARY WINDINGS, MEANS CONNECTING SAID SECONDARY TRANSFORMER WINDING AND SAID MOTOR WINDINGS IN AN ELECTRICAL CIRCUIT, MEANS CONNECTING SAID PRIMARY TRANSFORMER WINDINGS AND SAID SOURCE OF ELECTRICAL ENERGY IN AN ELECTRICAL CIRCUIT, SWITCH MEANS FOR BREAKING THE CIRCUIT BETWEEN SAID ELECTRICAL SOURCE AND SAID PRIMARY TRANSFORMER 